Portable devices, such as cell phones, are becoming increasingly common. These portable devices have grown more complex over time, incorporating many features including, for example, MP3 player capabilities, web browsing capabilities, capabilities of personal digital assistants (PDAs) and the like.
The battery life of these portable devices, however, can be limited. Often, the primary draw of battery power is the display device for these portable devices and, in particular, the backlight, which can be used to illuminate the display device. Thus, operation of these devices can be hampered by not turning off the backlight when it is not needed, such as when the device is held next to or against to the users head. Similarly, these devices can be hampered by performing unintended functions as a result of processing multiple unintentional inputs at an input device that contact a user's face or head.
Some of these portable devices may also include multiple sensors which are used to detect the environment or context associated with these portable devices. For example, U.S. patent application publication no. 2005/0219228 describes a device which includes many sensors, including a proximity sensor and a light sensor. The outputs from the sensors are processed to determine a device environment or context. The light sensor detects ambient light levels and the proximity sensor detects a proximity to an object, such as a user's ear or face.
This is shown in FIG. 1, which shows a device 10. The device 10 includes a proximity sensor 12 mounted on a surface of the device 10 and an ambient light sensor 14 also mounted on the surface of the device 10, such as near an earpiece or speaker. During operation, sensor 12 emits light having known characteristics (e.g., frequency, wavelength, and/or waveform) and detects the emitted light. A portion of the emitted light from sensor 12 hits an object and is reflected by the object, when the object is present above sensor 12. A portion of the reflected light is then received or detected by sensor 12 to determine the proximity of the object to sensor 12. However depending on the types, color, surface shape, and surface textures of materials of the object, the portion of reflected light can vary widely causing large differences in proximity sensor proximity determinations for objects at the same distance from sensor 12.